燃料电池中铂基电催化剂的设计与合成

燃料电池具有高能量转化效率、低环境污染等优势,近年来备受关注。然而,阴极氧还原反应和阳极小分子氧化反应成为燃料电池产业化的瓶颈,包括催化剂制备成本高、催化活性低和稳定性差等问题。如何设计高效、稳定的燃料电池催化剂,对于进一步推动燃料电池的应用十分关键,而发展先进的铂（Pt）基电催化剂是最为有效的途径之一。相比于单金属铂纳米晶,铂基无序合金和有序金属间化合物具有独特的物理化学特性,被认为是研究金属电催化剂结构-性能的理想模型。本文综述了高活性、高稳定性的铂基电催化剂的研究现状,首先阐述了铂基电催化剂的催化活性和稳定性的增强机制,着重介绍了铂基合金的调控因素与可控合成,进一步总结了铂基有序金属间化合物的制备策略。最后,对铂基电催化剂的未来发展方向进行了讨论及展望,以期为燃料电池中电催化剂的发展开拓新思路。     

核壳结构低铂催化剂:设计、制备及核的组成及结构的影响

核壳结构低铂催化剂具有可大幅提高贵金属铂的利用率、有效降低燃料电池铂使用量及成本的重要特点,被誉为质子交换膜燃料电池大规模商业化的希望之所在,相关研究已成为燃料电池领域最为热门的课题之一。本文综述了近年来提出的各种高性能核壳结构催化剂的设计思路及新型制备技术,介绍了各种不同组成和结构的核壳结构催化剂性能及特点以及在核壳结构催化剂表征技术方面的最新进展。最后对核壳结构催化剂制备技术的发展和应用前景进行了展望:通过发展或改进制备工艺,制备各种形貌组成可控以及高活性低Pt载量的核壳结构催化剂,有望实现质子交换膜燃料电池商业化。     

核壳聚合与核壳结构聚合物乳液

对核 /壳乳液聚合机理、方法、工艺以及核 /壳结构聚合物乳液的制备和性能进行了综述 ,重点讨论了各种因素对核 /壳结构聚合物乳胶粒子形态的影响 ,并回顾了核 /壳乳液聚合最新的研究动态。     

核壳结构催化剂在费托合成中应用研究进展

介绍了国内外用于费托合成核壳结构催化剂的研究现状,特别是具有核壳结构催化剂的应用,并对目前核壳催化剂中存在的问题进行了讨论,为今后的研究提出建议。     

核壳结构乳液研究进展

综述了核壳乳液聚合的发展、聚合工艺及影响因素,并对比了核壳结构与其他结构乳液在性能方面的优缺点,而且阐述了核壳结构的不足以及发展前景。     

质子交换膜燃料电池用Pt基核壳催化剂的制备及表征

催化剂性能的好坏对燃料电池催化剂性能起着至关重要的作用.近期的很多研究主要集中在具有双金属结构的催化剂纳米颗粒上,尤其是具有核壳(core-shell)结构的催化剂纳米颗粒.本文综述了国内外用于质子交换膜燃料电池的核壳结构催化剂的制备方法和表征方法的研究现状.     

核壳结构材料表征技术

本文对核壳结构共聚物进行了剖析，介绍了一些最常用的核壳结构表征技术．以大量文献为基础并结合笔者的经验．详细地阐述了这些表征技术的原理、方法、特点、局限性及改进方法，并结合核壳结构材料的应用，展望了核壳结构表征技术的发展趋势。     

贵金属负载型核壳结构催化剂的制备及其催化性能

以十六烷基三甲基溴化铵(CTAB)为表面活性剂,尿素为碱源,正硅酸四乙酯(TEOS)为硅源,在环己烷和正戊醇组成的微乳体系中制备了以微孔ZSM-5分子筛为核,树枝状介孔SiO_2为壳的多级孔核壳结构分子筛。考察制备温度、时间、尿素添加量以及TEOS添加量等制备条件对制备催化剂所需载体的影响,并采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和N2吸附-脱附等手段对分子筛样品进行了表征。结果表明,制备温度为100~120℃,时间为4 h,尿素与TEOS物质的量之比为1和TEOS与ZSM-5物质的量之比为0.9~1.2时,得到的核壳结构分子筛呈现出优良的单分散性、完整性以及水热稳定性。最终在树枝状介孔SiO_2壳层负载高分散贵金属Pt,得到的双功能催化剂Pt/ZSM-5@MS在催化丙酮一锅法制备甲基异丁基酮(MIBK)反应中表现出较高的活性及良好的循环使用性能。     

含环氧基核—壳结构乳液的性能

文中讨论了引入环氧基团，及环氧基团不同分布对乳液性能的影响，证明引入环氧基团，并采用核－壳结构将环氧基团分布于乳液聚合物颗粒的表面，能有效地提高乳液的性能。     

质子交换膜燃料电池催化剂性能增强方法研究进展

发展低成本、高性能的燃料电池催化剂是实现燃料电池商业化的关键。目前,铂基催化剂仍是动力燃料电池不可替代的主催化剂。本文综述了最近几年燃料电池催化剂增强方面的研究进展,探讨了新型催化剂材料的设计与制备以及提高催化剂活性或稳定性的方法,包括表面修饰、包覆、合金化、几何与电子结构以及晶体结构的调变、催化剂/载体相互作用等手段。开发高活性和高稳定性的非铂类催化剂是燃料电池催化剂的发展趋势和努力方向。其中,提高非铂燃料电池催化剂可靠性、稳定性和活性,迫切需要在燃料电催化理论、非铂催化剂理性设计、燃料电池水热管理、有序化膜电极等方面取得创新和突破。     

Mo oxide modified catalysts for direct methanol, formaldehyde and formic acid fuel cells

Pt black and PtRu black fuel cell anodes have been modified with Mo oxide and evaluated in direct methanol, formaldehyde and formic acid fuel cells. Mo oxide deposition by reductive electrodeposition from sodium molybdate or by spraying of the fuel cell anode with aqueous sodium molybdate resulted in similar performance gains in formaldehyde cells. At current densities below ca. 20 mA cm⁻², cell voltages were 350–450 mV higher when the Pt catalyst was modified with Mo oxide, but these performance gains decreased sharply at higher current densities. For PtRu, voltage gains of up to 125 mV were observed. Modification of Pt and PtRu back catalysts with Mo oxide also significantly improved their activities in direct formic acid cells, but performances in direct methanol fuel cells were decreased.     

核壳结构镍基纳米催化剂的制备及其在肉桂醛加氢反应中的性能

分别以硝酸镍和氯化镍为镍源,利用热分解法和水合肼还原法制得镍纳米粒子,再经模板剂造孔法在镍核外部包裹一层介孔壳,通过焙烧和氢气还原制备了核壳结构催化剂Ni@mSiO₂和Ni-N₂H₄@mSiO₂,并以肉桂醛加氢为探针反应考察了核壳结构镍基催化剂与负载型镍基催化剂的加氢性能。结果表明,核壳结构镍基催化剂在肉桂醛加氢反应中比共沉淀法制备的负载型镍基催化剂具有更高的活性,氢化肉桂醛的收率可达90%以上。同时,Ni-N₂H₄@mSiO₂催化剂具有较高的磁饱和度,可实现该催化剂在反应后高效回收并循环套用。采用X射线衍射、比表面及孔分析、透射电子显微镜、H₂-程序升温还原和H₂-化学吸附等表征手段,研究了所制催化剂的结构特征,初步探讨了催化剂结构与性能的构效关系。     

直接甲醇燃料电池阳极催化剂研究进展

直接甲醇燃料电池（direct methanol fuel cells, DMFC）由于其高效、清洁等优点,成为替代化石能源的理想新能源装置。催化剂作为DMFC中重要的组成部分,通过降低反应活化能,解决甲醇需要高过电势才能被电氧化的问题。但是目前DMFC阳极催化剂存在催化活性低、抗CO毒性差以及成本较高等问题,限制了DMFC的商业化。本文介绍了甲醇的催化电氧化原理,从Pt基催化剂、非Pt基催化剂、催化剂载体三个方面对DMFC阳极催化剂国内外研究进展进行了综述。介绍了通过选择合适晶面、添加助催化剂、制备特殊形貌、选择合适的载体4种方法对提高催化剂性能、降低催化剂成本的研究现状。甲醇在Pt（100）晶面上的催化活性较好但是抗CO毒性较弱;根据双功能理论和电子调变理论,制备的Pt-M合金催化剂具有更高的抗CO毒性和甲醇催化活性;非Pt基催化剂的制备为降低催化剂成本提供了研究思路;选择合适的催化剂载体,利用载体与催化剂之间的相互作用,也成为解决DMFC阳极催化剂目前面临的易中毒、活性低、成本高等问题的解决方法。     

Development of anode catalysts for a direct ethanol fuel cell

Ethanol electrooxidation was investigated at platinum based electrodes: Pt, Pt—Sn, Pt—Re dispersed on a high surface area carbon powder. The atomic composition of the bimetallic catalyst was varied and the best results were obtained with an atomic ratio Pt:X close to 100:20. The electrocatalytic activity of Pt, PtSn and PtRe was compared using cyclic voltammetry and long-term electrolyses at constant potential. Under voltammetric conditions and in a single direct ethanol fuel cell, PtSn was the most active catalyst. During electrolysis ethanol was oxidized to acetaldehyde (AAL), acetic acid (AA) and carbon dioxide. On PtSn/C and PtRe/C, the ratio AA/AAL was found to be always lower than unity. Otherwise, PtSn electrocatalysts were the most selective towards the production of CO₂ compared to Pt and PtRe electrodes.     

Optimum processing parameters to improve sealing performance in solid oxide fuel cells

Glass–ceramic composites are among the favorable candidates as a sealing material for solid oxide fuel cells (SOFC). In order to obtain a reliable, robust and hermetic sealing, the glass–ceramics must chemically bond to both the metallic interconnector and the ceramic electrolyte. A high-bonding strength and good wetting, which strongly depend on the thermal treatment, are always preferred to ensure gas-tight sealing. The thermal treatment involves three stages: binder burnout (stage-I), sintering (stage-II), and cooling (stage-III). This study investigates effects of various parameters on the sealing quality at the sintering stage. The effects of sintering temperature, clamping pressure and sealant thickness are considered. The glass–ceramic laminates are produced employing a tape casting method. The sealing quality is evaluated by measuring leakage and final macro-structure of the sealing region. It is suggested that a 900–930 °C sintering temperature and 1.5–7.6 N cm⁻² clamping pressure ranges are better for successful sealing. The initial thickness of glass–ceramic laminates is also desired to be between 0.25–0.5 mm thickness range for both a cost-effective and reliable sealing.     

Carbon supported Pt–Cr alloys as oxygen-reduction catalysts for direct methanol fuel cells

Electrocatalytic activities of various carbon-supported platinum–chromium alloy electrocatalysts towards oxygen reduction in 1 mol l⁻¹ H₂SO₄ and in 1 mol l⁻¹ H₂SO₄/1–3 mol l⁻¹ CH₃OH, were investigated by means of rotating disc electrode experiments and in solid polymer electrolyte direct methanol fuel cells. The activity of these electrocatalysts for methanol oxidation was evaluated using cyclic voltammetry. It was found that Pt₉Cr/C prepared by reduction with NaBH₄ exhibits the lowest activity for methanol oxidation and the highest activity for oxygen reduction in the presence of methanol, in comparison to commercial Pt/C, Pt₃Cr/C and PtCr/C electrocatalysts.     

Characterization of core-shell structured Ni@GDC anode materials synthesized by ultrasonic spray pyrolysis for solid oxide fuel cells

Core-shell structured NiO@GDC powders with NiO cores and GDC shells were synthesized by ultrasonic spray pyrolysis (USP) with a four-zone furnace. The morphology of the as-synthesized powders can be modified by controlling parameters such as the precursor pH, carrier gas flow rate, and zone temperature. At high carrier gas flow rates, the as-synthesized core-shell structured NiO@GDC powders have raisin-like morphology with a rough surface; this is due to fast gas exhaustion and insufficient particle ordering. The core-shell structured Ni@GDC anode showed considerable electrochemical performance enhancement compared to the conventionally-mixed Ni-GDC anode. The polarization resistance (R_p) of conventionally-mixed Ni-GDC anodes increases gradually as a function of the operation time. Alternatively, the core-shell structured Ni@GDC anode synthesized by USP does not exhibit any significant performance degradation, even after 500 h of operation. This is the case because the rigid GDC ceramic shell in the core-shell structured Ni@GDC may restrain Ni aggregation.     

Material aspects of the liquid feed direct methanol fuel cell

A study of a small scale Liquid Feed Direct Methanol Fuel Cell (LFDMFC), based on solid polymer electrolyte membrane, is reported. Two flow cell designs, one with a parallel flow channel arrangement and the other with a spot design of flow bed, are used. The structure of the DMFC comprises a composite of two porous electrocatalytic electrodes; Pt–Ru–carbon catalyst anode and Pt–carbon catalyst cathode, on either side of a solid polymer electrolyte (SPE) membrane. The performance of three Pt–Ru catalysts is compared. The influence of the degree of Teflon loading on the electrode structure is also reported. The effect of the following parameters: cell temperature, oxygen gas or air pressure, methanol liquid flow rate and methanol concentration on the power performance is described.     

碳化钨载铂的制备及其对硝基苯的电催化还原

以偏钨酸铵（AMT）为钨源前驱体,气流式喷雾干燥仪造粒,得到空心球状结构偏钨酸铵,固定床气固反应,以CO/CO₂为还原碳化气氛在800℃下制备了介孔空心球状碳化钨。采用氯铂酸作为铂源,用浸渍、气相还原法制备了Pt/WC粉末催化剂。通过XRD和SEM测试手段对Pt/WC粉末样品进行了表征,表明Pt成功负载在介孔WC材料上。采用循环伏安法、以Pt/WC粉末微电极为工作电极,研究了Pt/WC对在质子惰性介质中硝基苯的硝基还原的催化作用。结果表明,Pt/WC催化剂对硝基还原有着良好的电催化活性和化学稳定性。